I have the same problem. Apparently afpd crashes when a user successfully authenticates.
Maybe the following logs are useful:
Aug 16 04:50:14 rivendell avahi-daemon[26344]: Joining mDNS multicast group on interface eth0.IPv6 with address fe80::5604:a6ff:fe9d:5e22.
Aug 16 04:50:14 rivendell avahi-daemon[26344]: New relevant interface eth0.IPv6 for mDNS.
Aug 16 04:50:14 rivendell avahi-daemon[26344]: Joining mDNS multicast group on interface eth0.IPv4 with address 10.69.69.169.
Aug 16 04:50:14 rivendell avahi-daemon[26344]: New relevant interface eth0.IPv4 for mDNS.
Aug 16 04:50:14 rivendell avahi-daemon[26344]: Network interface enumeration completed.
Aug 16 04:50:14 rivendell avahi-daemon[26344]: Registering new address record for fe80::5604:a6ff:fe9d:5e22 on eth0.*.
Aug 16 04:50:14 rivendell avahi-daemon[26344]: Registering new address record for 10.69.69.169 on eth0.IPv4.
Aug 16 04:50:14 rivendell avahi-daemon[26344]: Registering HINFO record with values 'X86_64'/'LINUX'.
Aug 16 04:50:15 rivendell avahi-daemon[26344]: Server startup complete. Host name is rivendell.local. Local service cookie is 829140687.
Aug 16 04:50:16 rivendell avahi-daemon[26344]: Service "rivendell" (/services/afpd.service) successfully established.
Aug 16 04:50:27 rivendell afpd[26349]: AFP3.3 Login by nobody
Aug 16 04:50:27 rivendell afpd[26349]: volume "Home Directory" does not support Extended Attributes, using ea:ad instead
Aug 16 04:50:31 rivendell afpd[26349]: AFP logout by nobody
Aug 16 04:50:31 rivendell afpd[26349]: dsi_stream_read: len:0, unexpected EOF
Aug 16 04:50:31 rivendell afpd[26349]: afp_over_dsi: client logged out, terminating DSI session
Aug 16 04:50:31 rivendell afpd[26349]: AFP statistics: 0.14 KB read, 0.12 KB written
Aug 16 04:50:39 rivendell afpd[26352]: ===============================================================
Aug 16 04:50:39 rivendell afpd[26352]: INTERNAL ERROR: Signal 11 in pid 26352 (2.2.1)
Aug 16 04:50:39 rivendell afpd[26352]: ===============================================================
Aug 16 04:50:39 rivendell afpd[26352]: BACKTRACE: 3 stack frames:
Aug 16 04:50:39 rivendell afpd[26352]: #0 /usr/sbin/afpd(netatalk_panic+0x1c) [0x7fdd6c1d3aec]
Aug 16 04:50:39 rivendell afpd[26352]: #1 /usr/sbin/afpd(+0x50bec) [0x7fdd6c1d3bec]
Aug 16 04:50:39 rivendell afpd[26352]: #2 /lib/x86_64-linux-gnu/libc.so.6(+0x364c0) [0x7fdd6b1904c0]
Aug 16 04:50:45 rivendell afpd[26356]: AFP3.3 Login by nobody
Aug 16 04:50:45 rivendell afpd[26356]: volume "Home Directory" does not support Extended Attributes, using ea:ad instead
Aug 16 04:51:27 rivendell afpd[26367]: ===============================================================
Aug 16 04:51:27 rivendell afpd[26367]: INTERNAL ERROR: Signal 11 in pid 26367 (2.2.1)
Aug 16 04:51:27 rivendell afpd[26367]: ===============================================================
Aug 16 04:51:27 rivendell afpd[26367]: BACKTRACE: 3 stack frames:
Aug 16 04:51:27 rivendell afpd[26367]: #0 /usr/sbin/afpd(netatalk_panic+0x1c) [0x7fdd6c1d3aec]
Aug 16 04:51:27 rivendell afpd[26367]: #1 /usr/sbin/afpd(+0x50bec) [0x7fdd6c1d3bec]
Aug 16 04:51:27 rivendell afpd[26367]: #2 /lib/x86_64-linux-gnu/libc.so.6(+0x364c0) [0x7fdd6b1904c0]
There are likely more descriptive error messages in /var/log/system.log, which would help identify the problem. – Kyle Jones – 2012-03-16T20:00:36.083